1. Field of the Invention
The present invention relates to a lens composition for a light emission diode (LED) device, an LED device, a backlight unit, and a liquid crystal display (LCD) comprising the same, and more particularly, to a lens composition for an LED device, for an LCD having high transparency and high heat resistance, an LED device, a backlight unit, and an LCD comprising the same.
2. Description of the Related Art
In general, a liquid crystal display (LCD) is an image display device in which liquid crystal is injected into a space between two glass plates and power is applied to upper and lower electrodes installed at the two glass plates to thus vary the molecular arrangement of the liquid crystal at each pixel location. Such an LCD device largely includes a panel unit, a driving unit, and a backlight unit.
Unlike a cathode ray tube (CRT) or a plasma display panel (PDP), the LCD is not a self-luminescent display so that a display of the LCD cannot be achieved in dimly lit environments. To address this problem, that is, in order to operate an LCD device as a display device in a dark place, a backlight unit is utilized to provide uniform illumination onto an information display panel.
In particular, as the trend towards large-sized LCD devices grows, the use of a direct-type backlight unit, which generally provides a high luminance, will increase.
In a direct-type backlight unit, in which a light source is positioned below an LCD panel, a light guide plate (LGP) is disposed in front of the light source and a reflection plate is disposed behind the light source so that light emitted from the light source is diffused and reflected to then illuminate the LCD panel. Since the direct-type backlight unit efficiently utilizes light because of the presence of the reflection plate and the light guide plate, it can be effectively used in a backlight unit requiring high luminance.
As direct type backlight units are becoming increasingly smaller, thinner, and lightweight, a light emitting diode (LED) has been proposed to replace a cold cathode fluorescent lamp (CCFL) that is normally used. This is advantageous from the standpoint of superior luminance, lower power consumption and lower weight over devices that employ CCFL.
However, in the conventional backlight unit, multiple LED devices are arranged to achieve high luminance, resulting in an increase in the internal temperature of the backlight unit. That is, a temperature rise in the backlight unit using LED devices is approximately 1.5 times that of the backlight unit using CCFL as a light source.
Particularly, epoxy resin, which is a material used for a lens of the conventional LED device, is prone to deterioration due to such a large temperature rise. Accordingly, it is desirable to develop compositions suitable for the lens of an LED device in light of the trend toward increasingly larger-sized LCD devices.